I'm tempted to suggest that you put about a foot of gravel into the bed. It would not only accomplish the desired lowering, but the ride will be a lot smoother as well. Removing one or two leaves on each spring is the simplest, least expensive way, but only if you don't intend to carry heavy loads in the bed.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!